The present invention relates to hydrocarbon cracking catalysts containing yttrium and to the use of such catalysts in the cracking of hydrocarbon feedstock to maximize gasoline production.
Hydrocarbon cracking catalysts containing rare earth exchanged zeolites are in wide commercial use and their general technical properties have been reviewed in the literature, e.g. Fluid Catalytic Cracking with Zeolite Catalysts, Venuto and Habib, 1979 Marcel Dekker, Inc., pp. 30-49 and Chemistry of Catalytic Processes, Gates et al, 1979, McGraw Hill, pp. 49-57 and pp. 78-85. The commercial rare earth mixtures used for ion exchange with zeolites comprise cerium, lanthanum, prasodymium, neodymium and other rare earths including trace amounts of yttrium.
Hydrocarbon cracking catalysts comprising Y-type zeolites exchanged with rare earths have been disclosed in numerous patents including, for example, U.S. Pat. No. 3,436,357, Y zeolite exchanged with rare earth; U.S. Pat. No. 3,930,987, rare earth exchange including yttrium inter-alia.
U.S. Pat. No. 4,405,443, discloses that zeolite exchanged with rare earth, the mixed with yttrium and an inorganic oxide provides an absorbent for sulfur oxides.